The present invention relates to a dual roll blind system which is able to adjust a light shading rate or extent, and in particular to a dual roll blind system in which it is possible to easily adjust an indoor light shading function as a light transmission part and a light non-transmission part formed on two blind materials are overlapped by moving at least one of two blind materials in a left or right direction with the help of an operation chain, and it is possible to easily adjust an up and down height.
As disclosed in a Korean utility model registration number 20-0401004, a conventional blind system is designed to perform a light transmission, partial light shading, and full light shading operation by adjusting an overlapping of two sheets of a polarization screen by moving one of two winding rolls using a feeding part having a cam.
The conventional blind system is provided with a winding roll feeding apparatus which is formed of a horizontal movement cam shaft, a bracket, a chain wheel and an operation chain as well as a screen winding apparatus formed of a chain wheel and an operation wheel which rotate a winding roll. So, the structure is so complicated, and manufacturing the same costs too much. It is needed to separately operate the winding apparatus and the feeding apparatus, thus causing many inconvenience when in use. In addition, since a winding roll is pushed and fed with the help of a difference between a long direction size and a short direction size in a horizontal direction movement with a sliding friction contact in a horizontal direction with one surface of a gear in a state that an elastic force of a spring keeps being applied to a winding roll, the winding roll, which moves while compressing the spring, does not maintain a fed state by means of an increased elastic force of the spring, so that it may move in a direction that a user does not want. In addition, since it is impossible to feed a winding roll by a long distance due to its structure in a horizontal direction, a width of the vertical polarization part and the horizontal polarization part should be small at the polarization screen. So, when a light shading is present in a partial state, it is impossible to provide a much opening feeling.